Quick Facts

Mission Key Dates

Aug. 25, 2003 — The Spitzer Space Telescope (then called the Space Infrared Telescope Facility, or SIRTF) launches aboard a Delta 7920H rocket from Cape Canaveral Air Force Station in Florida. The spacecraft is launched into a solar, Earth-trailing orbit, far enough away from the planet so Earth's radiation does not interfere with the cooling of the telescope. The telescope’s dust cover was ejected Aug. 29 and its aperture door opened on Aug. 30.

Dec. 1, 2003 — SIRTF begins regular operations, following three months of in-orbit checkout procedures and verification of the spacecraft subsystems and science instruments.

Dec. 18, 2003 — SIRTF is renamed the Spitzer Space Telescope in honor of astrophysicist Lyman Spitzer, Jr. (1914-1997), one of the first people to propose the idea of using telescopes in space. The first Spitzer images and spectra are released to the public.

May 15, 2009 — Spitzer depletes its onboard supply of liquid helium, used to cool the telescope mirror to as low as 5.5 degrees above absolute zero, or 5.5 Kelvin (minus 450 degrees Fahrenheit or minus 267 degrees Celsius). This concludes Spitzer’s prime mission — also known as the “cold mission.” (The liquid helium supply lasted about 5 months longer than estimates made by the mission at launch, because of careful budgeting of the supply.)

July 27, 2009 — Spitzer’s first mission extension begins. Without liquid helium, the spacecraft’s passive cooling system keeps the telescope temperature as low as 28.6 Kelvin (minus 408 degrees Fahrenheit, or minus 244 degrees Celsius). Mission engineers are able to resume data collection using two out of four wavelength channels on the Infrared Array Camera (IRAC) instrument. (Infrared wavelengths are often referred to by their physical length; in this case, 3.6 and 4.5 micrometers, or microns. A micron is about one millionth of a meter.) This becomes known as the “warm mission.” The Infrared Spectrograph (IRS) instrument and the Multiband Imaging Photometer for Spitzer (MIPS) instruments cannot operate in this temperature range because the detectors warm up and produce overwhelming noise in the signal.

January 1, 2015 — The second Spitzer mission extension begins.

January 1, 2017 — The third Spitzer mission extension begins.

Oct. 1, 2017 — The fourth Spitzer mission extension begins. This period forward is dubbed the Spitzer Beyond Mission.

April 1, 2019 — The fifth and final Spitzer mission extension begins.

Jan. 30, 2020 — Mission engineers will place Spitzer into safe mode, and the project manager will declare the mission ended.


Height: 13 feet (4 meters) tall

Primary mirror size: 2.8 feet (0.85 meters) wide (about the diameter of a hula hoop)

Primary mirror composition: Beryllium (maintains its size at low temperatures)

Weight: 2,094 pounds (950 kilograms)

Wavelengths observed: 3.6 to 160 microns in cold mission mode (August 2003 - May 2009); 3.6 and 4.5 microns during warm mission mode (July 2009 - January 2020)

Telescope temperature: 5.5 Kelvin (minus 450 degrees Fahrenheit or minus 267 degrees Celsius) in cold mission mode; 28.6 Kelvin (minus 405 degrees Fahrenheit or minus 243 degrees Celsius) in warm mission mode


Infrared Array Camera (IRAC) — Imaging camera that captures 3.6, 4.5, 5.8 and 8.0 microns during cold mission mode; 3.6 and 4.5 microns during warm mission mode.

Infrared Spectrograph (IRS) — Provides high- and low-resolution spectroscopy at mid-infrared wavelengths (from 5 to 40 microns). Operated only while the spacecraft was in cold mission mode.

Multiband Imaging Photometer for Spitzer (MIPS) — Imaging camera and spectrometer that detects light in the far-infrared, at wavelengths of 24, 70 and 160 microns. Operated only while the spacecraft was in cold mission mode.

Areas of Science Exploration

Distant and nearby galaxies; the formation of stars and planetary systems; comets and asteroids; exoplanet detection and atmospheric studies; brown dwarfs; interstellar molecules and dust; black hole disks and jets; the cosmic history of star formation.

For more information about Spitzer’s science legacy, and past science press releases go here.


Mission classification: Class B, Category 2 (high priority), community observatory.

Cost: $776 million at launch (including launch costs). Total mission cost: $1.36 billion.